We use a custom extension that replaces the .dgn for our sheet files. We are finally upgrading to XM and we would like our custom extension to be listed as an option in the "files of type" filter on the open dialog. in previous versions, once you typed in the custom extension it would be added to the pull down list and then could be selected in later sessions of Microstation. We can change our user preferences by unchecking the option of "Use WindowsFile Open Dialogs" (under look and feel) and we are then given the same options as previous versions, but I would have to think that there should be a way to modify the list given when using the default dialogs.
Thanks for your help!
Add custom file types to List Files of Type:
http://www.askinga.com/tip.asp?TipID=425
OR:
http://communities.bentley.com/Communities/Other_Communities/AskInga/w/AskInga/add-custom-file-types-to-list-files-of-type.aspx